1. Field of the Invention
The present invention relates to auto focus cameras, and more particularly to an auto focus camera which causes a focus lens to change in position relative to a focus sensor by a predetermined amount at a time, and detects focusing-related components at respective positions, thereby effecting focusing control based on the detected focusing-related components.
2. Description of the Prior Art
In the conventional auto focus cameras of this kind, it has been a practice to effect exposure to a photographic subject and detect contrasts on the subject at respective relative positions. From the result of detection, AF evaluation values (focusing-related components) are calculated respectively for the relative positions, in order to determine as an optimal position a relative position at which a maximum AF value is available. That is, the AF evaluation values have a characteristic in a mountain-like form as shown in FIG. 12, wherein a summit thereof corresponds to a focal point. Due to this, the optimal position has been determined from a position at which the AF evaluation value assumes a maximum in value.
In such a prior art, however, the increase in amount of one relative position change also increases a deviation of a relative position corresponding to a maximum evaluation value from a focal point. As a result, there has been a problem that an optimal position even if once determined included deviation with respect to the focal point.